Montana experts help game wardens, tribal officials use fly larvae to nab poachers

Story contains images of animal carcasses

A decaying mule buck carcass. The deer was collected from roadkill by a government agency, then kept in a walk-in freezer in preparation for the training. It was then placed at the training site two weeks before the class began. (Al Barrus/USFWS)

A few miles off the interstate in the desert west of Albuquerque, an acrid fragrance rises among the prickly pear, cane cholla, and juniper plants. There, two large animal carcasses surrounded by a chain link fence ripen under the July sun. Dozens of game wardens, wearing uniforms representing tribal law enforcement groups from across the West, bear the stench with humor as they review training materials.

For today’s story we’re looking at how the study of insects and decomposition stages in forensic cases can lead to the arrest of criminal poachers. This is not the most glorious part of a game warden’s job, as it means examining rotting animal carcasses and collecting samples of maggots to determine time of death.

In July, the U.S. Fish and Wildlife Service Southwest Region hosted training for dozens of tribal game wardens from reservations across the country. The Region’s Native American liaison and former federal wildlife officer Joseph Early coordinated the training event funded by the Bureau of Indian Affairs (BIA).

“We have quite a variety of tribes here today. We have about 36 officers from around the Southwest. We have a few from California’s Hoopa Valley Tribe, Standing Rock Sioux Tribe from South Dakota, as well as Rocky Boy’s Tribe in Montana. The rest are Pueblo and Apache tribes from here in New Mexico and Arizona.

“We had two professionals from Montana and one from Idaho come down to teach a course in wildlife forensics. The scenario is you come upon a dead animal, and they’re teaching the game wardens and tribal rangers what to look for as far as evidence.

“This is good for the tribes because a lot of tribal officers don’t get this kind of training to begin with. They typically go through a basic police or BIA academy. They’re taught to be street cops, and then they’re put out in the field with maybe a little to no knowledge, unless they were raised on the reservation themselves, and they know how to hunt and fish.

“But they’re really not given the tools or the training to go out and investigate a wildlife kill or investigate a crime scene that’s involving a poached animal. So they get the training when they can. I worked closely with BIA who provided funding for this training, as well as with the Native American Fish and Wildlife Society to put this 40-hour training on for these tribal officers,” said Early.

A major theme of law enforcement for game wardens is the investigation of animals taken illegally for trophies. Often these laws are enforced by the Lacey Act of 1900, which prohibits the trade of wildlife that were taken illegally. Another is the Migratory Bird Treaty Act of 1918, and the Bald and Golden Eagle Protection Act.

“Many poachers are headhunters, looking for large antlered deer bucks or bighorn sheep. So the game wardens may come across a carcass missing the head, then adapt to investigate how the animal was taken. This training focuses on investigating cases where they might partner with U.S. Fish and Wildlife law enforcement, enforcing laws the Lacey Act, or Migratory Bird Treaty Act violation: catching people who are shooting hawks or eagles for feathers, which are used for tribal regalia to be sold on the black market. The cases vary from tribe to tribe,” said Early.

A species of carrion beetle forages around for blowfly larvae and pupa to feed on near a decaying bull elk carcass. (Al Barrus/USFWS)

This training was conducted by federal government contractor Wildlife Field Forensics. The definition of forensics is: the use of scientific tests or techniques to detect of a crime. The officers spent previous days in the classroom learning about the theories and techniques of forensics.

A big part of forensics field work is the preservation of crime scenes, protecting evidence from contamination, and collecting clues such as DNA and footprints. Field instruction also focused on the investigation of a rare yet devastating event: a wildlife attack on a human, setting up a scene with props and fake blood. Another instructor showed the officers how to extract ballistic evidence from a roadkill fox that had been shot post-mortem for instructional purposes.

What most stood out in the field environment was the ever present funk from the pair of carcasses enclosed by a chain link fence. A decaying mule buck and bull elk, provided by government agencies from road kill, then kept in walk-in freezers to prepare for the course. They had spent the two preceding weeks decomposing at the site to set the scene of a poaching.

This portion of the training was taught by Wildlife Field Forensics founder / director and former federal wildlife officer Carleen Gonder. When Carleen left the federal service she became a student, earning her master’s degree in criminology and forensics from the University of Montana.

“As a federal officer working poaching cases, I developed a strong interest in time of death, and in decomposition. My graduate work focused on decomposition over time, learning to do an estimate on time of death, because that’s usually when we find poached carcasses: long after the crime has been committed.

“Toward the end of my research I thought of creating this training, because when I was an active-duty law enforcement officer, I looked for crime scene investigation training specific to wildlife and nothing existed.

“So I thought about the idea of developing a program over a few days’ period bringing in experts from related fields, doing wildlife crime scene investigation training, and that’s how Wildlife Field Forensics was born. We did our first seminar in Montana during the Spring of 2007, and we’ve been doing it ever since. As far as I know, we are the only wildlife forensics training program in the country,” said Gonder.

Poaching, or the illegal take of wildlife, is a common type of crime that game wardens encounter. Usually, it’s carcasses they find, missing some key body parts, and the rest of the animal is left to rot.

Game warden and law enforcement rangers, when investigating a poaching case, can collect the insects feeding on a carcass, then send them to a lab where an entomologist (an insect scientist) can learn the time of death based on the bugs’ development. Forensic entomology is the study of insects as evidence in a criminal investigation. In her research on analyzing decomposition to estimate time of death, Carleen also learned to collect and preserve insects for entomologists.

Now she travels the country training conservation law enforcers to identify decomposition stages, collect and preserve insects, and the how temperature and moisture affect decomposition and insect development.

When it comes to insects, the main indicator for time of death are fly larvae, or maggots, as they’re usually the first insects to feed on a corpse.

With a group of officers going over their decomposition analysis checklist handout, she asks the students to inventory the tools they need for the collection.

This is where the story gets a bit gross, and you may want to stop reading at this point if you don’t want to go there.

“OK, so you’ve got your rubber bands, you’ve got your paper towels, you’ve got all your equipment. So what’s the first thing that you’re gonna do…? Glove up.”

“Throw up?” an officer quips. She nods “Throw up… believe me it’s not that bad.”

Going down the checklist procedure, they note the condition of the deer.

“This is past the bloat stage – remember, that’s the anaerobic: it’s a balloon filled with gas, and once it’s punctured by maggots or whatever, then it deflates, then it goes into the active decay stage,” said Carleen.

Both of these carcasses have already deflated, and maggots are pouring out from several orifices. They’re pouring out collectively, as a sort of liquid state. The class breaks into groups, and they began to go for the maggots. Another piece of evidence they need to collect is temperature.

“OK, so I’m gonna take the temperature. I’m just gonna lay the probe on top. And see they are pulling it down.” At this point the thermometer starts to sink into the glob of maggots is if it was a thick liquid. “I’m not pushing it. So that’s the temperature of your maggot mass. Then you’re gonna do ambient. Does someone wanna hand me that spoon?”

“Look at that fried rice,” one of the officers jokes. Carleen agrees “Yeah, we’re gonna have fried rice for lunch.”

With gloved hands wielding a regular plastic spoon, they scoop the maggots into evidence cups, tapping the spoon to shed all the larvae. Then they soak them in hot water, which kills them.

“They’re dead. And that plumps them up, makes them easier for the entomologist to look at them, and see the breathing spiracles on the butt end,” said Gonder. The spiracles indicate larval development.

Tribal game warden students examine maggots pouring out from the back end of a decaying mule buck carcass. The deer was collected from roadkill by a government agency, then kept in a walk-in freezer in preparation for the training, then put at the training site two weeks before the class began. (Al Barrus/USFWS)

Then they put the plumped maggots into alcohol to preserve them. They prepare another sterile cup with live larvae, giving them some meat to feed on, and enough air and room to survive the trip to the lab. In the process, they also record from which part of the carcass the maggots were collected.

There are several stages of maggot development, as well. Identifying the stages is important for an entomologist’s lab work.

“If it’s got pink in the crop, that’s blood, and it’s still eating. If it does not have a pink crop, and it’s moving far away from the carcass, that means it’s done eating and it’s pre-pupal,” said Gonder. When maggots pupate, they harden into a kind of cocoon. “See over here where that ground is darker? That can lead you to the pupal casings,” said Gonder. The casings are important to collect, as they’re the oldest maggot specimens. The adult fly moves away, but leaves its tell-tale cocoon behind.

These maggots are young blowflies: they’re the kind of flies with a green metallic sheen. They often show up minutes after something dies. They’re very sensitive to the fumes from corpses and dung, as that’s where their young thrive.

But the blowfly isn’t the only important insect indicator for time of death. Once rotten flesh is dried out, or desiccated, it’s difficult for maggots to eat. This is where the beetles come in. Not the fab four, these carrion specialists come fashionably late to the feast. They’re good at removing bits of meat off the bone. Some beetles are there just for the other bugs, predating on the plentiful maggots, and even on other beetles.

“So what are you going to do for the beetle collections? Remember, beetles are not site specific. They move around a lot, and they can be hard to catch. They’re really quick. You will collect them from all around the carcass, put them all in the same jar, and then you put them in alcohol,” she explains. “Remember, they eat each other. If you put them together alive, all you will have is one fat happy beetle and legs of all the other ones.”

Scooping up maggots and carrion beetles from the rancid putrefaction of decomposing flesh isn’t a pleasant part of a law enforcement officer’s job. However, the collection is just the beginning of the story for the forensic entomologist, whose results can shed light onto cases that would otherwise go unsolved. This field has been around since the 1930s, and is used primarily by homicide detectives.

“We work with an expert from Canada. She does work with the Royal Canadian Mounted Police (RCMP) doing human homicide cases, and now more and more wildlife. I’m kind of pinch hitting for her, and giving training in collecting those insects under the very strict protocols that entomologists require,” said Carleen.

“Temperature is what drives maggots, and they’re the prime determiner a forensic entomologist uses to determine time of death: to the day. Under different temperature ranges, the blowfly larvae take a certain period of time to develop through their three maggot stages, called instars,” said Carleen.

Maggots are pretty tolerant of cold temperatures. Some species have been observed surviving temperatures as low as 75 degrees below zero. In those frigid climes, they lie dormant in the carcass. When the mercury picks back up, by changing seasons or night and day cycles, the larvae become more active.

As their habitat gets closer to the upper 90s, they are able to eat and develop quicker. Determining an accurate outdoor temperature at the corpse takes a bit more field work.

“We put a data-logger at the poaching site that collects temperatures every 30 minutes over a two-week period. Then we compare the fluctuations to data from a nearby weather station. We backtrack and compute the differences of temperature prior to when we put that data-logger out, looking at the temperatures from the weather stations,” said Carleen.

Thermometer data loggers are very accurate, inexpensive, and easy to use. They’re basically USB sticks that the game warden leaves on the ground near the carcass site under a protective cover from the sun, with the east, west and north ends open to allow air flow, then plug into a computer and download 1,000+ temperature readings. This allows investigators to set up a sort of temporary weather station exactly where they find a carcass, to see how the temp shifts over a fortnight. Then they obtain data logs from nearby public weather stations.

They put the data sets together, plugging them into an algorithm that compares the readings to pair the timestamps. This turns out a ratio or average that makes it possible to go back in time, looking at the historic data from the public weather station. From that, they have a scientifically accurate estimate of what the temperatures were around the carcass during the course of the decomposition.

“And that’s what the forensic entomologist uses, is those range of temperatures to learn how long it took the maggots to get to that stage of development. It takes X days for this blowfly larvae to reach first instar, second instar, and so forth,” said Carleen.

While forensic entomology has been around for a while, it’s still a very niche field. Carleen’s program is one of only a few if not the only the only in the country to teach this field collection technique to game wardens and rangers. Insect collection in poaching cases isn’t widely practiced by conservation law enforcement.

Currently the U.S. Fish and Wildlife Service has all of their new federal wildlife officers go through two days of instruction in wildlife forensics, contracted through Carleen’s company. The Service doesn’t yet employ any forensic entomologists, so that’s contracted out as well.

“What I encourage people to do when they’re at our training is to contact the woman who we use from Canada for our training, and she can tell them who in their area is a member of that international organization of forensic entomologists that can give them a determination that would be admissible as evidence in court,” said Carleen.

That person from Canada is Gail S. Anderson, Ph.D. In 1997, two dead black bear cubs and the mother were found in Manitoba at a dumpsite near Winnipeg, their gallbladders removed. Bear bile is valuable in traditional Chinese medicine and demands a lucrative premium at market. Dr. Anderson had trained that area’s RCMP official who assisted the area conservation officer. They collected the insects from the dead cubs, and sent the samples back to the lab.

With Dr. Anderson’s testimony on the time of death for those cubs, investigators were able to learn the identity of the perpetrators. The poachers went to jail for their crimes.

“When officers go to law enforcement academy, they get all the cop stuff. We get firearms training, defensive tactics, case history training, but it’s all geared to human type crimes. Once they finish their training they aren’t getting a lot of wildlife specific training,” said Carleen.

“We are kind of a novelty at this point, but we’re still going. Every year at our May training in Montana, we have 50 plus attendees from state, federal, and tribal agencies, and that demonstrates a need. For the most part, conservation law enforcers don’t get this kind of training to investigate poaching cases.

“I don’t like to use the word ‘poaching,’ because it brings up the idea of hand-slap misdemeanor. And a lot of prosecutors and even judges think back to a bygone era, like 20 years ago to the hungry guy who’s just trying to feed his family.

“Illegal take of a wildlife species is a crime, and people who commit it are criminals. I think it needs to be taken more seriously.”

This story was published with the permission of the author. It previously appeared on USFWS Southwest region website.